Trying to use a DrawTite ModuLite to tow a trailer....need help getting 12V!!!!!

[belfert]

I use the Modulite, but my lighting is all 12 volt.  My battery compartment is directly in front of the engine so I was able to pick up a 12 volt feed in there even though my bus is primarily 24 volt.  I did have a problem with the Modulite not working last year and ran out to get another one, but it did the same thing.  Someone had reversed the connections to one of the llights in the bus.  We fixed that and now I have an extra Modulite.

Now, on an MCI you don't have 12 volt lighting and probably no easy way to get 12 volt power to a Modulite so I recommedn you build your own converter as recommended.

[Sean]

You can use 12 volt relays if you place a resistor in series with one of the relay coil wires.

Dave is right, but I suspect the resistor you need will be just as hard to find as the correct relay.

You would need a 105-Ohm resistor in series with each relay's coil if you use a typical automotive 12v relay such as a Tyco or Bosch.  However, it needs to be a 2-Watt rated resistor -- the little jobbies you can buy at Radio Shack are only 1/4-Watt and will burn out, as you discovered.

-Sean
http://ourodyssey.blogspot.com

(Edited to correct values -- I was looking at the wrong spec sheet)

[Ednj]

Check your Messages.

[bobofthenorth]

Dave is right, but I suspect the resistor you need will be just as hard to find as the correct relay.

You would need a 105-Ohm resistor in series with each relay's coil if you use a typical automotive 12v relay such as a Tyco or Bosch.  However, it needs to be a 2-Watt rated resistor -- the little jobbies you can buy at Radio Shack are only 1/4-Watt and will burn out, as you discovered.

Based on some recent experience which I have had shopping for resistors at Rat Shack    I can state that they do in fact usually have a decent selection of high wattage ceramic resistors in addition to the fractional wattage ones. 

[Sojourner]

Or you can run 2 12v relay in series for 24v and use the one of 2 relay contact. No problem what so ever. Resistor is more problem that 2 relays. However if you can find & get 24v version now than it less parts.

Sojourn for Christ, Gerald

[Nusa]

Finding stuff in stock at Radio Shack is always a crapshoot...but you can increase wattage ratings by running resisters in parallel. Of course you have to select higher resistances compensate for the loss of resistance.

http://www.radioshack.com/product/index.jsp?productId=2062320 = 470 ohm 1/2W 5% Carbon Film Resistor pk/5 for $0.99

4 of those in parallel would be 470/4 = 117 ohms at 0.5 x 4 = 2 watts. That's close enough to Sean's number to work, assuming his assumptions are correct.

Of course, if you find 24V relays, that's still the better solution.

[Fredward]

I've got one of Gumpy's systems installed in my MCI. It is a simple thing to install and everything always works the way it should. WHen you return from this trip I'd order one from Craig.  FWIW
FRed

[Gary '79 5C]

You maybe down the road by now, However if the OTR A/C has been removed, you have (2 -3) 24V Heavy Duty relays for the former evap and blower motors available for salvage.

On my 5C they were located in the forward bay, driver side mounted top of bay. Saved me $200 for two 200 amp used relays.

Good Luck, I looked around for a week before having my light to go on !!

Gary

[silverbusman]

go to a toyota dealer or any trailer supply store and buy a toyota land cruiser tail light converter. all you need to do then is put 24v bulbs in the two trailer sockets .
early cruisers were all 24 v.